1. Field of the Invention
This invention relates to a thin-film coil having a first coil and a second coil which are combined with each other, a magnetic head using the thin-film coil, a method of manufacturing the thin-film coil, and a method of manufacturing the magnetic head.
2. Description of Related Art
In these years, in view of high recording density of a magnetic recording medium, there is a need for improved characteristics of a magnetic head for recording on/reproducing from a magnetic recording medium. As an example of such a magnetic head, a composite thin-film magnetic head is often used which includes a recording head having an inductive type magnetic transducer for writing and a reproducing head having a magneto-resistive effect element for reading.
In such a thin-film magnetic head and a thin-film inductor, a coil is formed so as to generate a magneto-motive force. The coil is formed by means of a photolithographic process used for fabrication of semiconductor devices.
A coil formed by the process is generally referred to hereinafter as a thin-film coil. In a conventional method of forming a thin-film coil, a resist-film pattern P is formed in the shape of a coil as shown in FIG. 42A, a conductive film is then formed by plating and sputtering so as to obtain a thin-film coil L′ of a conductive film, as shown in FIG. 42B. In this case, a shape and a space between winding portions are defined by patterning accuracy of the resist-film.
The patterning accuracy of the resist-film depends on conditions such as resist-film materials and performance of fabricating apparatuses including applicators, exposing devices, and developing devices, for example. Some apparatuses used in semiconductor fabrication may provide a line-space less than or equal to 1 μm.
Unlike a thickness of a few nm in semiconductor devices, a thickness of a thin-film coil of a magnetic head and a thickness of a coil used in a thin-film inductor for a variety of converters are in a range of a few μm to 10's μm. It is very difficult to form a line-space less than or equal to 1 μm by using a resist film which is applicable to such a thick conductive film.
As shown in FIGS. 43A and 43B, two coils (an upper coil and a lower coil) are stacked or two-layered so that terminals thereof may be electrically connected to form a thin-film coil. Its thickness, however, increases and the thin-film coil may not meet miniaturization requirements.
Further, in a case where a width of a magnetic head is defined in response to requirements for high recording density on a magnetic recording medium and a width of winding portions of a thin-film coil is required to be within a predetermined value, the thin-film coil formed to have a width within the value is also required to be no more than a predetermined resistance. Accordingly, the thin-film coil should be formed so as to be of very high density, that is, better space factor.
Japanese Patent Application Publication Laid Open Hei 11-345404 discloses a magnetic head and a manufacturing method. The publication discloses a process for forming a thin-film coil of high space factor. In the process, a first coil and a second coil are formed on substantially the same plane.
In the process disclosed in the publication, an underlying film used to form the second coil remains between the first and second coils so that a short circuit is likely to happen between the remaining underlying film, electrically connected with the second coil, and the first coil. In other words, since there is only a very thin insulating film between the underlying film and the first coil, the insulating film may become too thin or broken by polishing, or some polishing refuse may cause a short circuit between winding portions. Further, undesirable capacity may be generated between the first coil and the underlying film and it may raise a serious problem in coil characteristics.